Woody crops are a potential source of fiber and biomass for energy. They can also be planted to reclaim contaminated soils, to protect sloping land against erosion, to act as a windbreak, or to create a buffer near sensitive waterways. Fast growing woody crops are an attractive proposition because of their widespread adaptation to various soils and climates and their short rotation. Some woody crops such as willow, poplar, aspen, alder, caragana and other species may be planted specifically for their short-rotation and their abundant biomass production. Several native species of woody plants (brushes) also grow naturally on abandoned land or near waterways.
There is a need to harvest regularly these woody crops for profitable uses of this fibre and biomass, and also to rejuvenate the vegetation. Typically, fast-growing woody crops are composed of a large number of stems ranging from 20 to 80 mm in diameter and 3 to 5 m in length after three years of growth. A three-year rotation is often considered the optimum cycle time to harvest for maximum yield over an extended life-cycle of 20 years and more for several perennial woody crops that spontaneously regrow after cutting. Conventional agricultural harvesters used for non-woody crops are not suitable for harvesting woody crops because they are not adapted for cutting through the relatively wide and hard stems of the woody crops. Also, the rigidity of the woody crop stems makes their baling more of a challenge.
For large area plantations of these woody crops, specialized cutter heads have been designed to cut the base of the woody crop stems and to feed the long stems into a precision-chop self-propelled (SP) forage harvester (U.S. Pat. No. 6,062,011). The SP cutter-chipper harvests woody crops in the form of chips which may be handled with augers and conveyors and stored in piles or silos.
One problem with the SP cutter-chipper is the relatively high cost of the machine, especially for small land owners. A second problem is the high moisture of the chips which form a dense pile with limited natural aeration and limited drying during storage. A third problem is the unsuitability of the SP cutter-chipper to harvest narrow strips of woody plants or to access uneven terrain with rocks or bumps where abundant brush may grow. Therefore, such a system works well for relatively large and flat areas, and where the 40 to 50% moisture content of the wood chips is acceptable, or where the wet chips can be dried artificially.
A number of attempts have been made to harvest woody crops in the form of bales which dry naturally to a greater extent than chips and which are easier to handle with a front-end loader readily available on many farms, thereby not requiring specialized augers or conveyors to handle the chips. U.S. Pat. No. 4,592,398 describes a system which cuts the stems, accumulates them on the side of the harvester and drops a bunch of stems on the side without tying or bundling. U.S. Pat. No. 5,377,479 describes a system which cuts the stems, conveys them in a bundle, slicing regularly, and tying the stems in relatively small bales. U.K. Pat. No. 2,357,417 describes a third system which proposes using a SP cutter-baler that ties large bales.
However, these prior systems are expensive, inefficient and not well suited for harvesting small areas. Therefore, it is desired to improve on these prior systems and to provide an efficient, low-cost baler-type harvesting device for woody crops to produce bales that can be handled easily, stored, and left to dry naturally during storage.